The arr_size() macro which is used to calculate the size of the chunk in the
array to be arranged resembles ARRAY_SIZE naming-wise. Avoid confusion by
renaming it to CHUNK_SIZE instead.

Also use min() macro to calculate the minimum of two numbers.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>